Method of etching on one



(M Model.)

5 J- BAYNEST l *METHOD 0F ETQHING 0N UNB oli-BOTH SIDES. f N0. 378,423. 'P'aentedf'eb 28, 1888.

A 'dumb UNITED f STATI-:sl

PATENT OFFICE.

JOHN nAYNns, or WEsToHEsTER COUNTY, NEW YORK.

METHOD oF Eroi-imc oN ONE" R BOTH sioas;

' SPECIFICATION forming part of Letters Patent No.`378.423. dated February 28, 1888.

Application ined May-2e, rsa1.

To all whom it may concern.-

Be it known that I, JOHN BAYNEs, a subject of the Queen of Great Britain, and a resident ot' WVestchester county, in the State of New vYork, United States of America., have invented \Vhcn it isdesired to perforate a comparalively thin plate of metal, marble, or other material,I have found that the same can be done by operating from one-side only of the plate, and in doing this I prepare one surface of the plate for the reception'of the pattern, which 1s applied in a coating of acid-resist, leaving the parts to be perforated free, so that the acid or other etching materialv may have access to the exposed parts. This resist-patternmay be applied in various ways, as by printing the same directly by the use of a lithgraphic press, or the resist-,pattern may be transferred lo the surface, or the vsurface may be completely covered with a resist made sensitive to light, and certain portions thereof rendered insoluble by the use of a Aproper negative in the ordinary photographic manner, and the soluble portions may be removed, leaving the acid-resist upon the surface in the desired conguration. This having been done,I coat the edges and back of the plate with the acid-resist and immerse the plate in a bath of etching material, or expose it to. the fumes of an etching-acid, or otherwise produce the perforations in the parts not covered by the acidresist. When, however, the plate is'too thick to be properly treated by etchingfrom one side, I cover both sides of the plate with the acidresist, exposing only those parts wherein it is desired Ito form the perforations, and it is evident that the patterns on the opposite sides of the plate must be the reverse of each other in order that the parts to be perforated vmay cor- Serial No. 239.554. (No model.)

respond and register with eachother. These reverse patterns in the acid-resist may-be applied in any of the ordinary ways, as by printing direct, transfer, or by photographing, as

before stated; but I have generally found it most convenient to use the photographic process and to coat both sides of the plate with the sensitive acid-resist, when, by the use of a A sist on leach side of the plate should correspond in those parts which are to be perforated,and

the parts which areto be in the form of rccesses only are produced in the acid-resist upon only one side of the plate, when the plate being treated to the etching process the perforations will be made by etching on both sidesof the plate and the recesses will be formed by etching on one side only. I have sometimes found it convenient-,in producing these perforations and recesses,to make asingle negative corresponding to all the portions to be etched, and from'this negative to produce the pattern in the acid-resist upon one side of the plate and then to produce a similar but reverse pattern in the acid-resist upon the other side of 85 l the plate, and'subsequently to stop out with a brush or otherwise the parts of the pattern which correspond with the recess portions of the pattern only.

It is Well known in etching perforations tions will not be the samethroughout the whole thicknessof the plate, as some portions-as those next to the surface-are exposed a longer time to the action of the etching material, and they will consequently be eaten away to a greater extent, leaving the perferations tapering to some extent. In order that the perforations may be of the same diameter on both sides of the plate, the pattern has to be pro- IOO 9c through a plate that the area of the pcrfora- 2 armas be etched.

When the plate is of considerable thickness and it is desired to have the perforations of a substantially uniform cross-section throughout l the thickness, and to preserve the face of the 1o metal sharp, and to prevent further side action upon the surface, I have found it advantageous to first cover the plate with the acidresist material in all portions except those corresponding tothe outlines of the perforations,

x 5 and to treat the plate to an etching process to eat in to the required depth the lines corresponding to the outlines of the perforations. These linesean then be filled with some acidresist which is insoluble in the same material 2o as the acid-resist afterward applied to the parts to be protected, and which conform to the pattern to be produced, and it is then evident that 'the edges of the openings will be protected by this insoluble resist,'and the perfo- 2 5 rations will'be produced with substantially the same cross-section throughout.

In the drawings, Figure 1 shows a plate coated with a resist,leaving the parts exposed which are to be perforated. Fig. 2 shows a 3o plate coated with a resist, leaving the parts exposed which are to be perforated, as well as those which are to be in the forni of recesses only, these parts being indicated by the shaded portions of the pattern, and it is understood that the opposite side of the plate is coated Awith a resist, leaving theparts exposed corresponding to the parts that are to be perforated only. Fig. 3 isa cross-section of a plate, showing'the manner of etching from both sides of 4o the plate, but to different depths; and Figs. 4

and 5 show a plate in .which the outline of the perforations is first etched and stopped out with an acid-resist material.

Referring toFig. 1, the plate is shown as covered with an acid-resist, A, leaving the portions B of the plate which are to be perforated uncovered, and, as before stated, this pattern may be applied by printing directly the pattern thereon in the resist material, or by trans- 5c ferring it thereto in the ordinary manner, or

- by first covering the whole plate with the sensitive resist and producing the pattern thereon by exposing the resist to light behind anegative plate containing a pattern corresponding to the parts to be perforated, and afterward washing each or otherwise removing the unsolidified parts of the resist.

The pattern shown in Fig. 2 may be produced by any of these processes, and two separate patterns may be employed, one correc, which are to be recessed and which are produced upon only one side of the plate; but I have found it more convenient and cheaper, as a general thing, to produce a single pattern-plate embodying both the portions to be perforated and recessed and to produeea pattern in the acid-resist from this on both sides of the plate and to afterward stop ont or paint out on one side the portions C,which are to be recessed upon the other side. y

When it is desired to etch the holes to a greater depth on one side than ,on the other, the acid-resist A upon one side of the plate, as D, Fig. 3, is applied so as tol leave the exposed parts B of substantially the size it is desired the perforations to be produced, while the resist A on the other side, E, of the plate 4is applied so that the portions B', which are to be etched are smaller than the corresponding spaces B, and as the acid eats away not only the bottom of the perforations but the sides thereof, the final result will be a perforation of substantially uniform cross-section, as indicated in the dotted lines F. In the above case, however, it is not possible to produce the perforations with perfectly unimaterials as the acid-resist A, which is afterward applied tothe parts to be protected, and which resist is preferably an asphaltum resist of the ordinary kind.

It will thus be seen that when the plate is exposed to the etching process the wax resist in the outlines G of the perforations will prevent the sidewise or widening effect of the etching, and the perforations will be practically the same configuration throughout, and the wax resist can be afterward removed by dissolving it in any proper solvent or by mechanical means.

What I claim is- 1. The process, substantially as hereinbefore set forth, of ornamenting plates, which consists in covering both sides of the plate with an acid-resist, in leaving the parts to be perforated exposed on both sides and the parts to be recessed exposed on one side only, and then subjecting the plate to the etching process.

2. The process, substantially as hereinbefore set forth, of ornamenting plates, which consists in coating both sides of the plate with an acid-resist, the parts of the plate to be perforated being exposed, the exposed parts ou one side being proportionately smaller than the corresponding parts on the other side, whereby when the plate is etched to different depths upon each side the perforations will be practically of a uniform cross-section.

3. The process, substantially as hereinbefore set forth', of ornamenting plates, which 5 by the solvents of the first resist, producing`V v Witnesses:l

consists in covering the plate with an acid-re- In testimony whereof Ihave signed my name sist at all portions except the outlines of the to this specification in the presence of two subpart to be perforated,\etehing said outlines, scribing witnesses.

filling said outlines with resist not aeeted JOHN BAYNES.l

the pattern thereon, and subjecting the same BERNARD J.- KELLY, to the etching process. P. KEMBLE, Jr. 

